This application relates generally to fiber optics and more specifically to fiber optic switching devices.
For high bandwidth fiber optics communication systems, an important functional requirement is the ability to switch optical signals with low loss and low crosstalk. That is, an effective optical switch should switch a significant fraction of the light to the intended channel and substantially none of the light to unintended channels. Crosstalk is typically expressed in terms of attenuation (measured in decibels or dB), and xe2x88x9250 dB is generally considered a target performance level. One such optical switch is a crossbar switch. A crossbar switch is a matrix of switching elements (also referred to as optical routing elements) for switching optical signals from a set of signal-carrying input optical fibers to a set of output optical fibers. A beneficial functionality for crossbar switching is having switching elements that are non-blocking, i.e., two optical signals traveling along different optical axis can pass through a switching element without either signal being blocked by the element. In addition to the functional performance characteristics mentioned above, it is desirable that the switch be fast, reliable, compact, and inexpensive.
Prior art optical switches include (1) opto-mechanical devices (using moving micro-optics), (b) thermo-optical polymer waveguides, (c) micro-electromechanical switches (MEMS), and (d) index matching fluid with movable bubbles in trenches in a planar waveguide. While all of these technologies have been demonstrated for optical switches, considerable efforts are still ongoing to develop an all optical switch matrix characterized by low loss and crosstalk, non-blocking, high speed and reliability, small overall size, and low cost.
As is well known, typical single-mode fiber optics communications are at wavelengths in the 1300-nm and 1550-nm ranges. The International Telecommunications Union (ITU) has defined a standard wavelength grid having a frequency band centered at 193,100 GHz, and other bands spaced at 100 GHz intervals around 193,100 GHz. This corresponds to a wavelength spacing of approximately 0.8 nm around a center wavelength of approximately 1550 nm, it being understood that the grid is uniform in frequency and only approximately uniform in wavelength. Implementation at other grid spacings (e.g. 25 GHZ, 50 GHz, 200 GHz, etc.) are also permitted. This frequency range and frequency spacings provides an enormous bandwidth for use in audio, video, audio-video as well as other communications needs such as the Internet and provides an impetus to develop optical technologies to exploit such bandwidth, such as switch matrices with characteristics as previously listed.
The present invention provides a non-blocking micro-optic switch matrix (NMSM) characterized by low insertion loss, low cross talk, ease of manufacture, and low cost.
The NMSM includes a plurality of optical routing elements (OREs) forming an Mxc3x97N matrix. The matrix has M rows and N columns, each row has N OREs and each column has M OREs. M and N may or may not be equal. Each ORE in a row may be optically coupled to the other OREs in the row, and each ORE in a column may be optically coupled to the other OREs in the column.
In one embodiment, each ORE has first and second wafer prisms that define a routing region. A gap disposed between the wafer prisms has a front and back bounded respectively by the first and second wafer prisms, and sides bounded by a pair of spacer elements. The gap is occupied by a thermal expansion element (TEE) that includes a body of material (such as polymer material) having contracted and expanded states at respective first and second temperatures. The contracted state defines an air gap disposed in the path of light traveling along a first optic axis that passes through both the first and second wafer prisms, such that the light is deflected by total internal reflection along a second optic axis that is at a non-zero angle with respect to the first optic axis. The expanded state removes the air gap so as to allow the light traveling on the first optic axis to pass through the first wafer prism and to further pass through the body of transparent material into the second wafer prism.
A further embodiment of the non-blocking micro-optic switch matrix is constructed of a silica wafer structure optionally disposed on a substrate. The silica wafer structure is formed with recesses or trenches in which the OREs are disposed.
In yet a further embodiment of the non-blocking micro-optic switch matrix, a first plurality of waveguide segments are optically coupled to a first optical routing element in each row of the Mxc3x97N matrix of OREs in a one-to-one manner. Additionally, a second plurality of waveguide segments are optically coupled to a last optical routing element in each column of the Mxc3x97N matrix of OREs in a one-to-one manner.
A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings.